1. Field of the Invention
The invention provides means for finding a support member hidden behind a building surface and for inserting a nail or similar fastener into the support member. In the preferred embodiment a composite tool for construction and remodeling of houses and other buildings is provided by the combination of a capacitive stud sensor with a carpenter 's hammer.
2. Background Information
Many buildings have walls, ceilings or floors constructed so that supporting structural members (e.g., wall studs) are concealed behind a surface (eg., a plasterboard wall panel). It is often desirable to determine the location of the hidden structural members--e.g., when one wishes to drive a nail into wall stud in order to hang a picture or other object on the wall. Many approaches to this problem have been proposed and used. These include tapping on the wall and estimating the stud 's location from the quality of the sound, as well as moving a pivotally-mounted permanent magnet along the wall to find the ferromagnetic nails or screws that a previous worker had used to hold up the wallboard.
Of particular interest to the present invention is the prior art of locating a hidden structural member by using a capacitive sensor responsive to a change in the effective dielectric constant of the wall created by the presence of that member. Notable among the prior patent art in this area are:
U.S. Pat. No. 4,099,118, wherein Franklin et al. teach a portable capacitive sensor to be moved along the wall and to visually indicate the proximity of a stud to an operator. PA1 U.S. Pat. No. 4,464,622, wherein Franklin teaches a capacitive stud sensor comprising improved adjustment and calibration means. The disclosure of Franklin is herein incorporated by reference. PA1 U.S. Pat. Nos. 4,853,617, and 4,992,741 wherein Douglas et al. teach an instrument comprising a metal detector and a capacitive sensor, the instrument also having a bar-graph display usable by the operator to more accurately determine the location of a hidden structural member. Douglas et al. also provide circuitry responsive to the AC power line frequency (e.g., 50 or 60 Hz) in order to warn the operator of the proximity of energized and unshielded electrical lines behind the wall. The teachings of Douglas et al. are herein incorporated by reference. PA1 U.S. Pat. No. 5,352,974, wherein Heger teaches an improved capacitive sensor that informs its operator when a wall is too thick or too thin for stud detection and when the operator has (incorrectly) calibrated the instrument by placing it over a stud, rather than over a section of the wall between two adjacent studs. PA1 U.S. Pat. No. 5,562,240, wherein Campbell teaches a tool comprising a nail gun, or the like, having a proximity sensor attached thereto, the composite tool further comprising a visual indicator to inform the operator when a firing end of the nail gun is aligned with a wall stud or other nail-receiving structural element.
Also of interest to the present invention is improved apparatus and method for making capacitive proximity measurements, as taught by the inventor in his U.S. Pat. No. 5,730,165, the disclosure of which is herein incorporated by reference.